In the exploration of oil, gas and geothermal energy, drilling operations are used to create boreholes, or wells, in the earth. Drill rigs used in subterranean exploration must be transported to the locations where drilling activity is to be commenced. These locations are often remotely located and in rough terrain. The transportation of such rigs on state highways requires compliance with highway safety laws and clearance underneath bridges or inside tunnels. Once transported to the desired location, large rig components must each be moved from a transport trailer into engagement with the other components located on the drilling pad.
Moving a full-size rig and erecting a conventional mast and substructure generally requires the assistance of large cranes at the drilling site. The cranes will be required again when the exploration activity is complete and it is time to take the rig down and prepare it for transportation to a new drilling site. Once the cranes have erected the mast and substructure, it is necessary to reinstall much of the machinery associated with the operation of the drill rig. Such machinery includes, for example, the top drive with mud hose and electrical service loop, AC drawworks, rotary table, torque wrench, standpipe manifold, and BOP. Movement of rig masts from transport trailers to engagement with substructures remains time consuming and difficult.
For the purpose of optimizing the economics of the drilling operation, it has become the practice to drill several directionally controlled wells from a single lease. As a result, the drill rig need only be moved a few feet. This optimizes the value of the lease, and vastly reduces down time from transportation. Offshore operations on fixed platforms made this common practice several decades ago, by placing drill rigs on a rail system, such as at THUMS Islands off the coast of Long Beach, Calif. However, in conventional land drilling operations, it is necessary to move the rig across natural terrain without minimal disassembly of the drill rig.
To achieve this movement, the conventional practice has been to use lifting pads at the corners of the base boxes. In this manner, a fully constructed drill rig can be moved a few feet at a time, until it is positioned over the next wellbore location. Drill rigs can be moved by means of lift pods for many years. Various patents have issued relating to drill rig relocation devices.
For example, U.S. Pat. No. 2,660,253 to Davidson describes an apparatus in which a platform rests on a base, with rails fixed to the underside of the base to provide horizontal travel and the base supported by vertical jacks. In operation, different sets of the jacks alternate extension and refraction. Hydraulics attached to the rails then move the base relative to a pontoon to move the entire platform in a forward direction. The device disclosed in Davidson leaves the rails that comprise the load bearing element and provide longitudinal displacement unprotected and exposed to the elements, which can lead to environmental contamination, increased friction, vibration, increased wear, and reduced life. The increased frictional load upon the rails eventually degrades horizontal travel performance of the apparatus.
U.S. Pat. No. 2,914,127 to Ricouard discloses a mobile platform for supporting heavy equipment comprising a chassis provided with a number of rollers rotatably mounted on spindles fixed to the chassis by supports. The rollers roll along a runway comprising a rigid rail with a base-plate forming a support face capable of supporting the machine. The machine operates by initially resting on the rails with the jacks supplied with pressure so as to extend and come into contact with the ground to raise the chassis. The chassis is then rolled along the track by way of the rollers. When the runway reaches the end of its travel, the chassis is lowered by acting on the jacks until the runways once again rest on the ground. The mechanism utilized by Ricouard poses a number of limitations, namely the rollers that bear the load of the chassis and provide horizontal locomotion of the mechanism are left unprotected and exposed to the elements, which would eventually accumulate contaminants and require maintenance. Contaminants and other debris present in the working condition of such machinery would also increase the variability of the friction forces opposing horizontal movement.
U.S. Pat. No. 3,576,225 to Chambers teaches a module and system for moving objects over the ground and employing separate modules that are supported by vertical jacks. The vertical jacks are extended, lifting the module off the ground. At least one of the vertical jacks further includes a sliding horizontal assembly slidable on a flat, lubricated interface. During operation, vertical jacks alternate support of the modules with the horizontal jacks, with horizontal movement of the module facilitated by shifting of the horizontal jack when the horizontal jack provides support for the module. In Chambers, the lubricated load bearing interface of the horizontal jack that supports the modules is directly exposed to the elements, and left unprotected to accumulation of dirt, rocks and other contaminants present in the environment. After passage of time, the lubricated interface may become contaminated due to such exposure, resulting in greater variable coefficient of friction and more difficulty for the horizontal jack to facilitate movement.
U.S. Pat. No. 6,581,525 to Smith teaches a load carrying transport apparatus for moving heavy loads, such as a drill rig. The apparatus of Smith provides a substructure for carrying the rig, including a pair of spaced apart frame structures which support the rig and an elongate track or sub beam, which is positioned on the surface, and upon which the frame structures are rolled along when lifted. Lift assemblies with associated rams and roller assemblies on the ends provide both vertical support and horizontal movement. The roller assemblies include a plurality of rollers rotatable around a horizontal axis, similar to a caterpillar track. The main beams are then displaced by rolling them along the sub beams that are laid on the surface beforehand for moving the rig. Due to the design of Smith, the roller assemblies that bear the load of the transport apparatus are in close proximity to the ground surface and left unprotected from dust, dirt and other elements. As such, the roller assemblies will eventually become worn and obstructed as foreign matter accumulates and grinds against the roller assemblies. This leads to eventual required maintenance and repair which renders the apparatus unavailable for some time.
Furthermore, several other prior art references also make use of various roller assemblies or related mechanisms to bear the load of the structures during the horizontal movement of the transportation or relocation apparatuses. For instance, U.S. Pat. No. 3,807,519 to Patch discloses a walking mechanism for moving a ground-engaging device over open terrain which uses one example of such a roller assembly. The mechanism of Patch includes support pads and plates. The plate and support pad are provided to permit longitudinal movement relative to the device. Roller means are disposed between the plate and pad to support the mechanism and facilitate longitudinal movement. The roller means include a plurality of longitudinally aligned rollers secured as a unit by channels through associated center axles.
Another instance of a prior art disclosing a roller assembly for longitudinal movement is U.S. Pat. No. 5,921,336 to Reed, which discloses a walking substructure device with a plurality of lifting jacks, with each jack having an upper end connected to the substructure and a lower end connected to a roller assembly which bears the weight of the lifting jack, and consequentially, the substructure. The apparatus of Reed operates to move the substructure by incremental displacement of the substructure via the roller assembly. The roller assembly supports the walking substructure and rolls on a center beam of a jack pad. A push-pull mechanism in the form of a pair of hydraulic cylinders extends between each jack pad and roller assembly in order to move the roller assembly relative to the center beam.
U.S. Pat. Nos. 7,681,674, 7,806,207 and 8,051,930 to Barnes each teach a walking vehicle for positioning and transporting relocatable equipment. The vehicle has at least four walking assemblies attached to a frame, with a pad attached to the surface contacting end. The walking vehicle of Barnes further discloses a push-pull traveling system for providing the movement of the walking assembly. The weight of the walking vehicle is supported by a roller assembly located in a housing with a central collar. During operation, the push-pull traveling system of Barnes pushes the rollers of the roller assembly, like a tank tread on top of a roller bearing surface. In this fashion, the vehicle can walk in a first direction.
In the Patch, Reed and Barnes series of references, the mechanism for bearing the load of the device is by way of a set of rollers, which are not sealed to the elements and may eventually become affected by debris and other materials present in the environment which the devices operate. As a result of the substantial load being placed upon the rollers, the rollers are susceptible to the additional particulates, which may create additional frictional forces between adjacent rollers. This leads to more variable coefficient of friction at the roller contact surfaces wherein one load bearing assembly may become more difficult to translate in a horizontal direction, thus adversely affecting the synchronous movement of the entire structure. What is needed then is a walking assembly that can facilitate horizontal movement evenly throughout the entire movement and maintain the assembly in a contaminant-free environment so as to prevent the contamination problems typically associated with the prior art.
It remains highly desirable to transport a drill rig short distances in a manner that avoids contamination of the frictional sliding surfaces with environmental elements. It is also desirable to transport a drill rig short distances with multiple devices that provide consistent and low frictional resistance at each device. For this purpose, it is also desirable to provide a system that includes a lubricant reservoir in communication with the sliding surfaces. It is further desirable to have the reservoir fully sealed from the surrounding environment. It is also desirable to have a device that is stable and self-centering, without external guides. It is also desirable to provide a device with a smooth sliding action that avoids vibration from irregularities. It is also desirable to have a device having a slide mechanism with a low vertical profile.
In summary, the preferred embodiments of the present invention provide a unique solution to the engineering constraints and environmental challenges of providing a durable, low-profile rig moving system that is protected from environmental contamination and provides a smooth, low friction sliding, low-energy action that prevents damage to the drill rig and the rig moving system.